Horsehair

January 01, 2022

During the first rainfall I encountered after moving to Arkansas I noticed several long thin worms wriggling on the driveway.  I assumed they were some sort of long worm, and probably parasitic.  Since We still had Bella, I was worried whether this could cause her problems, or even if the worm had come from her and been deposited on the grass.  When we took her to the vet, she checked out fine and got her quarterly deworming.  Studies show that prevalence of intestinal worms in dog populations can be as high as 54.3%, depending on location, and these can spread to humans.  The worms looked like a long horsehair from the mane.  They went away when the water dried up, and off my mind.  They frequently appear after rains and did so again last week.  I asked my gardener friends and they confirmed they have seen them as well, and only after a good rain.  I decided to find out what they were.

When I looked online, I found horsehair worms are insect parasites that belong to the phylum Nematomorpha (round worms), and one of the most common species of these worms in the US is Gordius robustus.  The body of the horsehair worm is extremely long and thread-like.  They are creamy to blackish in color and are frequently twisted and coiled like a discarded thread.  Not much is known about the life of horsehair worms.  The stage seen most common are adults who may appear late summer or fall in streams and ponds.  They are more commonly noticed in domestic water containers such as bird baths, swimming pools, water troughs, pet dishes, sinks, bathtubs, and toilets, but they may also be found on damp garden soil or vegetable plants after a rain.  Or in my case, on the driveway.  Despite their scary appearance, these species are not harmful.

Horsehair worms are about the size of a kite string (1/25 to 1/16 inch or 1 mm to 1.3 mm wide) and are very long (4 to 14 inches or 10 to 35.5 mm).  Amazingly, the entire horsehair worm grows and develops as a parasite inside the body cavity of large insects like crickets, grasshoppers, katydids, beetles, and cockroaches.  This internal parasite of insects does not harm humans, animals, or plants.  Because horsehair worms are parasitic, they are assumed to be beneficial in control of certain insects, but their value as a parasite is questioned as the worm does not kill its host until it matures.  The creatures are primarily of interest as one of nature’s oddities.

Thoughts:  Horsehair worms resemble hairs from horses actively moving in the water. A superstition once surrounding the species held the worms in water troughs and puddles had miraculously come to life from the long, thin hairs of a horse’s mane or tail that had fallen into the water.  The worms often squirm and twist in the water, knotting themselves into a loose, ball-like shape, resembling the “Gordian Knot,” so another name for horsehair worm is Gordian worm.  The Gordian Knot is a legend of Phrygian Gordium associated with Alexander the Great.  It is often used as a metaphor for an intractable problem (untying an impossibly tangled knot) solved easily by finding an approach to the problem that renders the perceived constraints of the problem moot (“cutting the Gordian knot”).  Both superstitions surrounding the horsehair worm illustrate finding a simple solution to a complex problem.  In the same way, there is a simple solution to the complex problem of the pandemic.  Get vaccinated and wear a mask.  Follow the science.  Change is coming and it starts with you.